1. Field of the Invention
The present invention relates to a magneto-resistance effect head used as a reproducing head of a magnetic recording/reproducing apparatus and a magnetic recording/reproducing head thereof.
2. Description of the Related Art
In recent years, high density recording systems such as a VCR with a recording density of 500 MB/inch2 and a HDD with a recording density of 200 MB/inch2 have been practically used. In addition, increase of the recording density is further being required. As a reproducing head for use with such high density systems, a magneto-resistance effect head (hereinafter referred to as an MR head) using a magneto-resistance effect of which the electric resistance of such as a magnetic thin film, a magnetic multi-layer thin film, or the like varies by an external magnetic field is becoming attractive.
FIG. 22 is a perspective view showing a construction of a conventional shield type MR head. In FIG. 22, reference numeral 1 is a substrate composed of Al2O3.TiC or the like. A lower shield layer 3 is disposed on the substrate 1 through an insulation layer 2. The shield layer 3 is composed of permalloy or the like. The insulation layer 2 is composed of Al2O3 or the like. A magneto-resistance effect film (hereinafter referred to as an MR film) is disposed on the lower shield layer 3 through an insulation film 4. The insulation film 4 forms a reproducing magnetic gap. A pair of leads 6 are connected to both edges of the MR film 5. As a result, a magneto-resistance effect device 7 (hereinafter referred to as an MR device) is formed. An upper shield layer 9 is disposed on the MR device 7 through an insulation film 8. The insulation film 8 forms a reproducing magnetic gap. A signal magnetic field is detected by the shield type MR head in the following manner. A sense current is supplied to the leads 6 and then the device resistance that varies corresponding to the variation of the direction of the average magnetization of the MR film 5 is measured.
When a signal magnetic field of for example a metal type recording medium is detected by the above-described shield type MR head, the MR head tends to short-circuit the metal type medium. Thus, a large amount of current flows in the MR device 7, thereby destroying the MR head. In addition, when the MR film 5 is machined in the depth direction, the MR film 5 directly comes in contact with an abrasive solution or the like. During the process, the MR film 5 gets corroded.
On the other hand, to prevent the above-described shield type MR head from short-circuiting the metal medium, an insulation protecting film is disposed on the medium opposite surface of the MR head and the medium front surface. However, this method is improper for a low flying that is necessary for improving the linear recording density. In addition, when a contact recording method that is becoming attractive as a future high density recording technology is used, since the medium opposite surface wears out and thereby the protecting film is lost. Thus, to solve such a problem, proper countermeasures should be taken. Moreover, when the MR device 7 wears out, the width in the depth direction varies and thereby the head output fluctuates. In this case, the MR film 5 may wear out and thereby it is lost.
As a head construction that prevents such a problem of the above-described shield type MR head, a so-called yoke type MR head as shown in FIG. 23 is known. In this yoke type MR head, the magnetic yoke 10 directs a signal magnetic field to the MR device 7 that is disposed in the head. In the yoke type MR head, the MR device 7 is disposed on a soft magnetic substance layer 11 that is a part of the magnetic yoke 10 through an insulation film 12 that is a magnetic gap. Soft magnetic substances 13 and 14 that are a part of the magnetic yoke are connected from the medium opposite surface to the soft magnetic substance layer 11 in the head through the MR film 5. In the yoke type MR head, the reproduced output decreases depending on the position of the MR device 7 and the connection of the magnetic yoke 10. In addition, these overlap lengths L0V fluctuate due to an alignment error between each of the soft magnetic substances 13 and 14 that is a part of the magnetic yoke and the MR film 5, and thereby the reproduced output fluctuates. Thus, it is difficult to produce MR heads with equal characteristics at a high yield rate.
On the other hand, a structure as shown in FIG. 24 has been disclosed. In this structure, a magnetic core 15 is disposed in the layer direction of the substrate 1. The MR device 7 is disposed in the magnetic core 15. The magnetic permeability in the direction of the film thickness of the magnetic core 15 is almost zero. In addition, the MR device 7 is recessed from the medium facing surface for the film thickness of the magnetic core 15. Thus, the reproduced output decreases. Moreover, since the production process of a magnetic yoke for such a yoke type MR head is complicated, it is difficult to reduce the production cost.
As described above, in the conventional shield type MR head, due to a short-circuit with the metal medium, the head is destroyed. In addition, during the production process, the MR film gets corroded. Due to wear-out of the MR device, the depth thereof varies. Thereby, the head output fluctuates and the MR film is lost. On the other hand, the reproduced output of the conventional yoke type MR head is small and fluctuates. In addition, the production process of the MR head is complicated and the production cost cannot be easily reduced.
The present invention is made from the above-described point of view. An object of the present invention is to provide a magneto-resistance effect head and a magnetic recording/reproducing head thereof for suppressing the fluctuation of the reproduced output due to the fluctuation of the depth and overlap length of the yoke to the MR film and for obtaining a good reproduced output at a low cost.
A first aspect of the present invention is a magneto-resistance effect head, comprising a magnetic yoke comprising a first magnetic yoke member and a second magnetic yoke member, wherein the first and second magnetic yoke members are disposed with a magnetic gap being between the first and second yoke members at a medium facing surface of the magnetic yoke, a magneto-resistance effect film connected to a pair of leads and disposed on a major surface of the magnetic yoke members at a position recessed from the medium facing surface by a predetermined distance, and the major surface being substantially in parallel with a magnetic flow from the recording medium to the first magnetic yoke member, the magneto-resistance film, and the second magnetic yoke member in this order.
A second aspect of the present invention is a magnetic recording/reproducing head, comprising a reproducing head constructed of the magneto-resistance effect head of the first aspect of the present invention, and a recording head including a magnetic core and a recording coil disposed through a magnetic gap and is constructed of an induction type magnetic head having a magnetic core and a magnetic gap that are shared with the magnetic yoke and the magnetic gap of the magneto-resistance effect head.
According to the magneto-resistance effect head of the present invention, since the magneto-resistance effect film is disposed on a plane of a magnetic yoke composed of a pair of magnetic substance (for example, along the upper surface of the magnetic yoke in the layer direction), a magneto-resistance effect film can be disposed at a position as close as possible to and recessed from the medium facing surface (namely, at a position adjacent to the medium facing surface). Thus, without loosing the advantages of the yoke type magneto-resistance effect head, much magnetic flux can be directed to the magneto-resistance effect film so as to obtain a highly reproduced output. Even if the medium comes in contact with the head and thereby the head wears out, the fluctuation of the output can be reduced as described later. Thus, since the overlap length between each of the magnetic substances that are the magnetic yoke and the magneto-resistance effect film can be satisfactorily large regardless of the recess position of the magneto-resistance effect film from the medium facing surface, the fluctuation of the reproduced output can be reduced.
Moreover, since the track-width is defined by the thickness of the yoke, narrow track of 1 xcexcm or less can be easily fabricated by using the film yoke.
The recording head and the reproducing head of the magnetic recording/reproducing head of the present invention can share the magnetic gap and at least a part of the magnetic head of the magneto-resistance effect head and the magnetic core of the induction type magnetic head. Thus, the track width and the gap length in the recording operation are the same as those in the reproducing operation. Consequently, since the alignment error between the recording and reproducing operations becomes zero, the recording/reproducing characteristics of for example a high density recording system can be improved.
These and other objects, features and advantages of the present invention will become more apparent in light of the following detailed description of best mode embodiments thereof, as illustrated in the accompanying drawings.